The present invention relates to wireless telecommunications in general and, in particular, to a terrestrial telecommunications system that employs an electronic scanning antenna that rotates a narrow antenna beam in synchronism with time-division multiplexed (xe2x80x9cTDMxe2x80x9d) and time-division multiple access (xe2x80x9cTDMAxe2x80x9d) data streams.
It can be prohibitively expensive to provide wireline telecommunications service in sparsely-populated regions. Therefore, it would be advantageous if a low-cost telecommunication system could be devised that would enable service to be provided to those areas at an affordable cost. Moreover, in regions where customers legally have a choice of service providers, such a system could facilitate the entry of additional service providers.
Cellular telecommunications equipment is often considered for such xe2x80x9clocal-loopxe2x80x9d applications, but in some circumstances it may not be suitable because of range limitations. A conventional cellular system typically employs a plurality of geographically dispersed base stations, each of which services a distinct geographic area called a xe2x80x9ccell.xe2x80x9d Each base station in a cellular system typically employs either: (1) an omnidirectional antenna, which transmits into and receives from the entire cell, or (2) several directional antennas, which each transmit into and receive from a different azimuthal sector of the cell.
The result is that the range at which a base station can service a wireless terminal is typically limited to 10 miles. This range can be increased by increasing the power at which the signals are transmitted, but this can be prohibitively expensive and the increased ambient radiation can jeopardize the public""s safety.
Another disadvantage of a conventional cellular system is that it cannot be used in an area that has a substantially allocated frequency spectra. It would therefore be desirable if a wireless telecommunications system could be devised that would radiate so little power that it would only minimally interfere with other signals at the same frequencies.
A typical embodiment of the present invention uses an electronic scanning antenna to rotate a beam that carries communication messages between a base station and a plurality of wireless terminals. A base station transmitter transmits the communication messages to each wireless terminal, via the electronic scanning antenna, in a time-division multiplexed (xe2x80x9cTDMxe2x80x9d) data stream that is synchronized with the rotation of the beam, and a base station receiver receives the communication messages from each wireless terminal in a time-division multiple access (xe2x80x9cTDMAxe2x80x9d) data stream that is also synchronized with the rotation of the beam.
In accordance with this embodiment, RF power is transmitted to a given wireless terminal for only a small fraction of the time, which thereby decreases the average power density incident upon each of the wireless terminals. Therefore, a higher peak transmitter power can be used at the base station to provide substantially improved range as compared to prior art systems.
Typical embodiments of the invention are also advantageous because they can be employed in geographic regions that have a substantially allocated frequency spectra, because the low average RF power radiated by the embodiments reduces the likelihood of interference with other signals.